TLS-RPT
SMTP TLS Reporting: a TXT record that asks sending mail servers to report TLS negotiation failures back to the domain owner.
TLS-RPT (SMTP TLS Reporting) is published as a TXT record at `_smtp._tls.example.com` and tells sending mail servers where to send daily aggregate reports about TLS connection attempts to the domain. Reports include successful sessions, failed STARTTLS negotiations, certificate mismatches, and MTA-STS policy violations. Without TLS-RPT, a misconfigured MTA-STS policy or expired certificate on a mail server can silently break inbound mail with no visibility. With it, the domain owner finds out within 24 hours which senders saw which failures, and from where.